The metallic tantalum powder was successfully synthesized via reduction of tantalum pentoxide (Ta2O5) with magnesium gas at 1073~1223 K for 10 h inside the chamber held under an argon atmosphere. The powder obtained after reduction shows the Ta–MgO mixed structure and that the MgO component was dissolved and removed fully via stirring in a water-based HCl solution. The particle size in the tantalum powder obtained after acid leaching was shown to be in a range of 50~300 nm, and the mean internal crystallite sizes measured by the Scherrer equation varied from 11.5 to 24.7 nm according to the increase in reduction temperatures. The temperature satisfactory for a maximal reduction effect was found to be 1173 K because the oxygen content was minimally saturated to about 1.3 wt %.
It was tried to find the optimal condition to prepare the metallic niobium powder with minimal oxygen content by atmospheric magnesiumgas reduction of niobium pentoxide (Nb 2 O 5 ) powder at 10731223 K, which are industrially moderate and low temperature ranges until maximally 80 h inside the chamber held under the argon circumstances of 110 kPa. Magnesium oxide of the by-product of the reduction, was dissolved and removed fully by dissolving in a 10% aqueous hydrochloric acid solution. The particle size of the niobium powder reduced for 20 h was slightly increased within the range of 200³600 nm according to increase of reduction temperatures. And such fine particles were further coarsened to near 1 µm by increase of reduction times until 80 h at 1173 K, which is thought to be the most suitable for magnesium-gas reduction to be applied in industry. The reduction time satisfied for a maximal reduction effect was found to be 60 hours as the oxygen content was then minimally saturated to about 0.42 wt.%. Furthermore, the hydrogen contamination due to acid leaching of 0.28 wt.% was fully removed by dehydrogenation, which was a heat treatment performed under vacuum at 827 K for 2 h; this resulted in the formation of metallic niobium powder.
Hexane is a safe, efficient, and cost-effective alternative to other commercial hydrocarbons for gaseous carburization; however, commercial hexane is not sufficiently pure. Titanium powder can remove oxygen-containing impurities from commercial hexane; however, research on the use of titanium powder remains limited. We investigated the purification of hexane using titanium, copper, and aluminum powders and used the purified hexane for the gaseous carburization of tantalum. Ti exhibited lower activation energy for oxidation (1.55 kJ/mol) than Cu (91.09 kJ/mol) and Al (150.25 kJ/mol) and a significantly higher oxidation rate (0.0269 g/h) in hexane at room temperature than Cu (0.0018 g/h) and Al (0.0001 g/h). The carbon content in tantalum carburized using the purified hexane was comparable to that carburized using unpurified hexane (approximately 6.22%); however, its oxygen content was significantly lower (1.39%), which indicates that the produced tantalum carbide has a higher purity. X-ray diffraction results revealed that the oxidation products of tantalum, such as Ta2O, TaO2, Ta0.8O2, and Ta2O5, were absent in the sample carburized using the purified hexane. Therefore, Ti powder can effectively remove oxygen-containing impurities from commercial hexane and facilitate its use as an effective carburizing medium for the synthesis of high-purity tantalum carbide.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.